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Nervous System > Spinal Cord and Periphery > Flashcards

Spinal Cord and Periphery Flashcards

1
Q

On the spinal cord, where is the grey and white matter in relation to each other?

A

Central grey matter and peripheral white matter

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2
Q

Where do axons of sensory fibres enter the spinal cord?

A

Through the dorsal root into the dorsal horn of grey matter

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3
Q

Where are the cell bodies of motor neurons in the spinal cord?

A

Ventral horn

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4
Q

What are the 3 columns of white matter in the spinal cord?

A

Posterior

Lateral

Anterior

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5
Q

What is found in each column of the spinal cord?

A

Various bundles (tracts) of xons

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6
Q

What kind of tracts are ascending pathways?

A

Sensory

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7
Q

What kind of tracts are descending pathways?

A

Motor

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8
Q

What are 3 important tracts of the spinal cord?

A

Corticospinal/pyramidal tract

Posterior/dorsal column

Lateral spinothalmic tract

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9
Q

What does the corticospinal/pyramidal tract carry?

A

Motor impulses from motor cortex to skeletal muscles

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10
Q

What does the posterior/dorsal column carry?

A

Touch, tactile localisation, vibration sense, proprioception

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11
Q

What does the lateral spinothalmic tract carry?

A

Pain and temperature

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12
Q

Where does the corticopsinal/pyramidal tract begin?

A

Motor cortex (area 4)

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13
Q

Do corticobulbar fibres go to the ipsilateral or contralateral nuclei?

A

Contralateral

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14
Q

Where do the corticospinal fibres decussate?

A

Decussation of pyramids

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15
Q

What are the different corticospinal tracts?

A

Lateral and anterior corticospinal tract

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16
Q

Do the anterior corticospinal tracts decussate?

A

No, only the lateral

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17
Q

What does the lateral and anterior corticospinal tracts innervate?

A

Lateral - limb muscles

Anterior - axial muscles

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18
Q

What are the fibres before anterior/lateral corticospinal fibres called?

A

Corticobulbar fibres

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19
Q

What are the 2 types of neurons in the corticospinal tract?

A

Upper motor neuron

Lower motor neuron

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20
Q

What is the site of the lower motor neurons?

A

Ventral horn

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21
Q

What are the common characteristics of pathways reaching conscious level (ascending spinal tracts)?

A

There are 3 neurons between peripheral receptor and cortex

Receptor -> first order neuron -> second order neuron -> third order neuron -> contralateral parietal cortex

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22
Q

In ascending spinal tracts, where is the first order neuron?

A

Dorsal root ganglion

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23
Q

In ascending spinal tracts, where is the second order neuron?

A

Grey matter of spinal cord or nucleus in medulla

24
Q

In ascendign spinal tracts, where is the third order neuron?

A

Nucleus in contralateral thalamus

25
Q

Does sensory information from ascending spinal tracts go to contralateral or ipsilateral side?

A

Contralateral parietal lobe

26
Q

What is the process of the posterior/dorsal column transmitting information?

A
  1. 1st order neuron ends by synapsing with the cell body of 2nd neuron which is situated in lower part of medulla
  2. 2nd order neuron crosses over (decussates) in medulla
  3. Tract is now called medial lemniscus and passes through the medulla, pons and midbrain to reach the thalamus
  4. Third order neuron starts from thalamus and axons pass through the IC and radiate to the post-central gyrus (area 2, 1, 3)
27
Q

What is the posterior/dorsal column called after it decussates in the medulla?

A

Medial lemniscus

28
Q

What is the function of the lateral spinothalamic tract?

A

Used for pain and temperature

29
Q

What is the process of the lateral spinothalamic tract transmitting information?

A
  1. First order neuron enters into the grey matter and ends at the same level
  2. 2nd order neurons cross over to reach the lateral column and is now called lateral spinothalamic tract
  3. 2nd order neuron ends in thalamus and 3rd order passes through IC, radiation to reach post-central gyrus
30
Q

Where does the deccusation of lateral spinothalamic tract occur?

A

At the level where it enters the spinal cord, not the medulla

31
Q

What is a reflex?

A

Involuntary stereotyped pattern of response brought about by a sensory stimulus

32
Q

What spinal level are most reflexes mediated at?

A

Level of the spinal cord (spinal reflexes)

33
Q

Anatomically, what are the different kinds of reflexes?

A

Monosynaptic (such a stretch reflex)

Polysynaptic (such as flexor reflex)

34
Q

What are some different kinds of reflex?

A

Stretch reflex

Flexor (and crossed extensor) reflex

35
Q

Explain the process of the stretch reflex (and reciprocal innervation)?

A

1) Tendon stretched
2) Intrafusal muscle fibres stimulated
3) Sensory neuron activated
4) Monosynaptic reflex arc, and also polysynaptic reflex arc to inhibitory interneuron
5) Muscle contraction, and reciprocal innervation

36
Q

What is the stretch reflex important for?

A

Control of muscle tone and posture

37
Q

Explain the process of the flexor reflex?

A

1) Pain stimulus
2) Sensory neuron activated
3) Polysynaptic reflex arc
4) Flexion and withdrawal from noxious stimulus, and also crossed extensor response to contralateral limb (only in weight bearing limbs)

38
Q

Do upper or lower motor neurons mediate reflexes?

A

Lower motor neurons

39
Q

What happens to reflexes if LMN is not affected in an UMN lesion that causes paralyses?

A

Reflexes are exageratted

40
Q

How does an upper and lower motor lesion impact the tone of a muscle?

A

Upper - increased tone (spasticity)

Lower - flaccidity

41
Q

What is spasticity?

A

Muscles continually contracted

42
Q

What is flaccidity?

A

Muscles lacking firmness

43
Q

If the lesion is above the level of decussation, are the signs and symptoms for the tone of a muscle contralateral or ipsilateral?

A

Contralateral

44
Q

If the lesion is below the level of decussation, are the signs and symptoms for the tone of a muscle contralateral or ipsilateral?

A

Ipsilateral

45
Q

What effect does a left UMN lesion of the corticospinal/pyramidal tract at internal capsule?

A

Right sided paralysis

Hyper-reflexia

Increased tone

46
Q

What effect does a left UMN lesion of the corticospinal/pyramidal tract at cervical spinal cord have?

A

Left sided paralysis

Hyper-reflexia

Increased tone

47
Q

What effect does a left LMN lesion of the corticospinal/pyramidal tract have?

A

Left sided paralysis

Absent reflexes

Flaccid

48
Q

What impact do LMN and UMN lesions have on reflexes and muscle tone?

A

UMN - hyper-reflexia and increased tone

LMN - absent reflexes and flaccid tone

49
Q

What is motor neuron disease (MND)?

A

Group of diseases affecting the lower motor neurons in the ventral horn of the spinal cord

50
Q

What happens to the neuron and muscle in MND?

A

Neuron dies and as a result the mucle supplied by it atrophies

51
Q

For posterior/dorsal column lesions, what does a lesion at left interal capsule cause?

A

Right sided (contralateral) sensory loss

52
Q

For posterior/dorsal column lesions, what does a lesion at left cervical spinal cord cause (below decussation)?

A

Left sided (ipsilateral) sensory loss

53
Q

For the lateral spinothalamic tract, what does a lesion at the left internal capsule cause?

A

Right sided (contralateral) pain and temperature loss

54
Q

For the lateral spinothalamic tract, what does a lesion at the left cervical spinal cord cause?

A

Right sided (contralateral) sensory loss

55
Q

What is the difference in the number of neurons in the ascending and descending pathways?

A

Ascending sensory tracts have 3 neurons in their pathway

Descending motor tracts have 2 neurons in their pathway (upper and lower)

Nervous System (48 decks)

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